1. Field of the Invention
The present invention relates to layout designing method of a display device.
2. Description of the Related Art
In a liquid display device using a TFT (thin film transistor) as a switching element, for instance, four panels 12 are prepared on a sheet of glass plate 11 as shown in FIG. 1. Each of the panels 12 is divided into, for instance, four shot areas (A, B, C, D) as shown in FIG. 2.
FIG. 3 shows a panel 12 in an enlarged form. In FIG. 3, in a display section of each of the shot areas 12a, 12b, 12c, and 12d indicated by the signs A, B, C, and D, a TFT switching pattern 13, a pixel pattern 14, or the like are formed as shown in FIG. 4. The TFT switching pattern 13 is formed with a layer construction consisting of 3 to 7 layers with such components as a gate bus line 13g or a drain bus line 13d. 
In the layout designing method based on the conventional technology, at first panel data concerning TFTs or pixels in a display device is prepared, and then one sheet of panel 12 is divided with a division tool or the like into a plurality of shot areas 12a, 12b, 12c, and 12d. However, if the gate bus line 13g or drain bus line 13d is divided at a place where a switching performance of a transistor
is badly affected, or if one pixel pattern 14 is divided into two sections, characteristics of the pixel at such a place changes, which in turn may cause non-uniformity in display.
To prevent generation of this non-uniformity in display, it is necessary to divide a G layer in which the gate bus line 13g is formed along a first division line Axe2x80x94A evading the gate electrode section as shown in FIG. 5. Regarding I layer in which the drain bus line 13d is formed, it is necessary to divide this I layer along a second division line Bxe2x80x94B evading the source/drain area. Regarding Px layer in which the pixel pattern is formed, it is necessary to divide this Px layer along a third division line Cxe2x80x94C so that a single pixel will not be divided.
In other layers not shown in these figures, there are line positions suited to division, and the division line positions are generally different from layer to layer. In other words, it is impossible to divide one panel into a plurality of shot areas by setting the same division line for all layers.
Therefore, in the conventional technology, appropriate division line is set for each layer. Following procedure is employed when manufacturing a display device. That is, as shown in FIG. 6, reticules 13a, 13b, 13c, 13d corresponding to the shot areas 12a, 12b, 12c, 12d indicated by the signs A, B, C, D are prepared for each layer, and exposure is made to resist applied on the glass plate 11 using these reticules 13a, 13b, 13c, and 13d successively and with an exposure device such as a stepper.
The layout designing method based on the conventional technology is described below with reference to FIG. 7 to FIG. 15B. FIG. 7 is a flow chart showing a flow in reticule preparation based on the conventional type of layout designing method. FIG. 8 to FIG. 15B show examples of geometrical patterns so that the flow chart above can easily be understood.
The examples of geometrical pattern shown in FIG. 8 are based on the assumption that a panel 21 is divided into four sections and comprises two layers, namely a G layer in which a heart-shaped pattern 22 is formed and an I layer in which a square pattern 23 is formed. As shown in FIG. 9, G1-G2 and I1-I2 are division lines for the G layer and I layer respectively. It is assumed that there occurs no functional problem in the panel pattern shown in the figure.
When layout designing is started, at first, panel data is prepared as shown in FIG. 7 (step S1). FIG. 8 shows a panel image prepared based on the panel data. At the next step, all layers are divided into a plurality of areas respectively (step S2). FIG. 9 shows divided images of all layers, namely the G layer and I layer in this example.
Images for the shot areas obtained by dividing the panel are located in data concerning the reticule image, thus a reticule image being prepared (step S3). Process patterns such as an alignment mark are prepared at the same time.
At the next step, a single layer, for instance, the G layer is divided (step S4). FIG. 10 shows an image 24 of those obtained by dividing the G layer to four sections. FIG. 10 to FIG. 15B show only GA and IA shot areas positioned at the light upper section of the FIG. 9 together with the G layer and I layer. A shading band (described as blind pattern hereinafter) and an auxiliary pattern are added to a section around the four images obtained by dividing the G layer (step S5) FIG. 11 shows a state where a blind pattern 25 is added to a divided image for the shot area GA in the G layer.
At the next step, whether all of the layers have been divided or not is determined (step S6). In this example, as the I layer has not been divided, the processing at step S4 is executed to divide the I layer. FIG. 12 shows an image 26 of the shot area IA among the four areas obtained by dividing the I layer. At the next step, a blind pattern and an auxiliary pattern are added to a section around the four images obtained by dividing the I layer (step S5). FIG. 13 shows a state where a blind pattern 27 is added to a divided image 26 of the shot area IA in the I layer.
The processing from step S4 to step S6 is repeated until all of the layers are divided, and when all of the layers are divided, preparation of designing data is finished (step S7). FIG. 14A and FIG. 14B show the prepared designing data 28, 29 for the G layer and I layer respectively.
Based on the prepared designing data, exposure data and reticules are prepared (step S8). FIG. 15A and FIG. 15B show exposure data and reticules 30, 31 for the G layer and I layer respectively.
In the layout designing method based on the conventional technology as described above, the processing for division is executed by setting divided areas for each layer taking into account a switching pattern or a pixel pattern, so that the processing for division is required to be executed repeatedly until all layers have been divided. Time required for dividing one layer is around 1 hour. Therefore, for instance, for a 15-inch display device comprising 5 layers about five hours are required until the processing for dividing all of the layers is finished.
Therefore, although reduction of production cost and designing cost for a display device is strongly desired recently, it has been difficult to reduce the designing cost.
It is an object of the present invention to provide a layout designing method of a display device which makes it possible to shorten time required for designing a display device and also to reduce the designing cost.
To achieve the object described above, in the layout designing method of a display device according to one aspect of the present invention, when designing a display panel comprising a plurality of layers and designed by dividing each layer to a plurality of short areas, a suspected division area is set so that shot areas corresponding to all layers are included, all of the layers are divided in batch along the suspected division area, and by treating a portion not included in a shot area of each layer in the suspected division area obtained as described above, an unnecessary portion is hid.
In the layout designing method of a display device of another aspect of the present invention, when designing a display panel comprising a plurality of layers and designed by dividing each layer to a plurality of short areas, all of divided areas in all layers are aligned to each other by aligning other layers to a reference layer, and all of the layers are divided in batch along the aligned areas.
Shot areas are positioned at reticules by offsetting each shot area by a rate of displacement of other layers to the reference layer. Or, a rate of displacement of other layers to the reference layer is given as an offset rate in exposure to an exposure device.
According to the invention, as all of layers can be divided in batch, the time required for division can be shortened, and further the reduction cost can be reduced.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.